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.\"     @(#)setregid.2	8.2 (Berkeley) 4/16/94
.\"
.Dd $Mdocdate: February 5 2015 $
.Dt SETREGID 2
.Os
.Sh NAME
.Nm setregid
.Nd set real and effective group IDs
.Sh SYNOPSIS
.In unistd.h
.Ft int
.Fn setregid "gid_t rgid" "gid_t egid"
.Sh DESCRIPTION
The real and effective group IDs of the current process
are set according to the arguments.
The saved group ID will be set to the new value of the real group
ID if a real group ID is specified and either
the new real group ID value is different from the current value
or the new value of the effective group ID differs from the
current saved group ID.
.Pp
Unprivileged users may change either group ID to the current value
of the real, effective, or saved group ID.
Only the superuser may make other changes.
.Pp
Supplying a value of -1 for either the real or effective
group ID forces the system to substitute the current
ID in place of the -1 parameter.
.Pp
The
.Fn setregid
function was intended to allow swapping the real and
effective group IDs in set-group-ID programs to temporarily relinquish
the set-group-ID value.
This purpose is now better served by the use of the
.Xr setegid 2
function.
.Pp
When setting the real and effective group IDs to the same value, the
.Xr setgid 2
function is preferred.
.Sh RETURN VALUES
.Rv -std
.Sh ERRORS
.Bl -tag -width Er
.It Bq Er EPERM
The current process is not the superuser and a change
other than changing the effective group ID to the real group ID
was specified.
.El
.Sh SEE ALSO
.Xr getgid 2 ,
.Xr setegid 2 ,
.Xr setgid 2 ,
.Xr setresgid 2 ,
.Xr setreuid 2
.Sh STANDARDS
The
.Fn setregid
function conforms to the
.St -p1003.1-2008
specification, except that the conditions for changing the saved
group ID differ and that, if it is changed, the saved group ID
is set to the real group ID instead of the effective group ID.
.Sh HISTORY
The
.Fn setregid
system call first appeared in
.Bx 4.1c ,
predating POSIX.
A semantically different version appeared in
.Bx 4.4 .
The current version, with the original semantics restored, appeared in
.Ox 3.3 .
